1. Field of the Invention
This invention relates to new devices used for temperature measurement, especially in corrosive environments, and to a method of use of the same. Preferred embodiments of the devices include improved, fast response, measuring devices for indicating temperature in corrosive chemical process streams.
2. Background of the Invention
It has long been desired to provide methods and devices for determining temperatures in corrosive environments. However, due to the hostile nature of such environments, the use of conventional temperature measuring devices has not proved to be satisfactory.
The measurement of temperature in corrosive, hostile environments has been accomplished to date using protective sheaths or thermowells. This protective enclosure can be designed to protect the temperature sensing elements from almost any corrosive environment, however, a serious compromise attends the use of the sheath leading to slow response. Commercial temperature sensors for corrosive environments have response time greater than one second. In many chemical processes this response speed is not adequate.
The invention described below relates to fabricating the temperature sensor from materials which are among the most corrosive resistant materials available: ruthenium oxide and iridium oxide. Their outstanding corrosion resistance has led to their use in geothermal brines at temperatures above 100.degree. C., See generally, "Electrically Free-Standing IrO.sub.x Thin Film Electrodes For High Temperature, Corrosive Environment pH Sensing", I. Lauks, M. F. Yuen and T. Dietz, Sensors and Actuators, 4 (1983), p. 375, and as charge injection electrodes, see "Stabilization of RuO.sub.2 by IrO.sub.2 For Anodic Oxygen Evolution", R. Kotz and S. Stucki, Acid Media, Brown Boveri Research Center, CH-5405, Baden, Switzerland, the entire disclosures of which are herein incorporated by reference.
In addition, by fabricating these temperature sensing electrodes as thin films their response can be in the microsecond range. The response characteristics of thin film thermocouples has been determined separately and reported by D. Burgess, Jr., M. Yust and K. G. Kreider, "Transient Thermal Response of Plasma-Sprayed Zirconia Measured with Thin-Film Thermocouple", Sensors and Actuators, A24 (1990), pp. 155-161, the entire disclosure of which is herein incorporated by reference.